Design, Fabrication, and Preliminary Testing of a Double Pipe Heat Exchanger

Author : Daipan, John Agustin
Major Adviser : Acda, Reynaldo I.
Committee Members : Valencia, Sixto A.; Arquiza, Apollo C.
Year : 1996
Month : May
Type : Thesis
Degree: BS
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A laboratory scale double pipe heat exchanger was designed, fabricated and tested.

The main materials used in the construction of the said equipment were copper tube of the size 3/4″ for the inner tube and GI pipe of the size 2″ for the outer tube. Screwed and inter-locked fittings and valve system were used as accessories. The total length was divided into four sections connected in series-parallel arrangement.

During the testing, hot water was allowed to pass inside the inner tube while the cold water was flowed co-currently and counter-currently through the annular space. The preliminary run involved the conditions set for the design: Tₕᵢ = 185 °F, T?ᵢ = 91.4. ; Wₕ = 5 mL/s, W? = 170 mL/s. Likewise, ten actual runs were made, five each for counter-current and co-current flow. At the same inlet temperatures, Wₕ was held constant at 20 mL/s, while W? was varied from 170 mL/s, 100 mL/s, 50 mL/s, 20 mL/s and 5 mL/s, respectively.

The over-all heat transfer coefficient increases as the flow rates of the streams were increased. U was highest at W? = 170 mL/s and lowest at W? = 5 mL/s, 22.86 (BTU/ft °F) and 6.8 (BTU/ft °F), respectively.

Likewise, the ratio between the fluid of lower flow rate to the fluid of higher flow rate was found to be inversely proportional to the heat exchanger effectiveness. Results showed that the heat exchanger effectiveness was highest for the design condition and lowest at W? = 20 mL/s., 89.5% and 37%, respectively.

On the other hand, percent heat loss was the lowest for heating systems W? = 20 mL/s and 5 mL/s. and highest for cooling system W? =  100 mL/s results were 5.5, 6.4 and 39 percent losses, respectively.

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